1. Field of the Invention
The present invention relates generally to the packaging of semiconductor devices. More particularly, the present invention relates to a reduced thickness semiconductor optical communication device package and a method of fabricating the same.
2. Description of the Related Art
In general, optical communication is a method by which information is transmitted and received by means of light.
When information is required to be transmitted, the information is first converted to an electrical signal, which is then converted again to a communication signal and then sent to a laser diode, that is, a light-emitting diode. The laser diode converts the electric communication signal to an optical signal, which is then transmitted through an optical fiber. An apparatus for converting the electric signal to the optical signal and transmitting the optical signal to the optical fiber is called a transmitter. After being outputted from the transmitter and then transmitted through the optical fiber over a long distance, an amplification circuit restores the original attenuated signal wave, which is then converted to an electric signal by a photo detector for detecting the light, that is, a light receiving element. The light receiving element, which plays the opposite role to that of the transmitter, is called a receiver.
In the light transmitter and receiver, the most important component is an optic semiconductor package, a light coupling module, which converts the electric signal to the optical signal and the optical signal to the electric signal. The optic semiconductor package includes optical elements such as a laser diode and a photo detector, optical fibers, and parts for packaging the optical elements and fibers.
Two kinds of methods, active alignment and passive alignment, are generally employed in coupling the optical fiber for transmitting light with the optical elements. Presently, the optic semiconductor package employing active alignment is mostly utilized. In the optic semiconductor package by the active alignment, an optical element is usually adhered to a substrate, and the optical element and the substrate are electrically connected with each other by a conductive wire. Thereafter, a metal can, to which a glass is attached, is coupled to the substrate over the optical element, and the optical fiber is adjustably fixed to the glass attached to the metal can. Thereafter, the position of the optical fiber is precisely adjusted according to a change of the electric signal or the optical signal after the optical element is operated, and the optical fiber is completely fixed to the metal can in an optimal optical coupling state by means of laser welding, soldering, or epoxy adhesion.
In the conventional optic semiconductor package as described above, the optical fiber and the optical element can be stably fixed in relation to each other, and measurements can be easily carried out. However, due to the thickness of the substrate, the optical element, and the conductive wire, the metal can has an increased height, thereby increasing the volume of the package itself. The above-mentioned conductive wire has a fixed loop height relative to the upper surface of the optical element, and the loop height puts a restriction on minimizing the distance between the optical element and the glass. The relatively large distance between the optical element and the glass deteriorates the optical coupling efficiency. Moreover, in the conventional optic semiconductor package, since a wire bonding has to be carried out to an optical element of a very small size (several hundred xcexcm), a very precise wire bonding apparatus is necessary, and the manufacturing process is complicated and the manufacturing cost is increased.
In accordance with the present invention, an optic semiconductor package includes a plate shaped substrate having an insulation layer through which two spaced apart layer apertures are formed. The substrate further includes a plurality of electrically conductive patterns formed on the wall surfaces of the layer apertures and a lower surface of the insulation layer. One of a laser diode and a photo detector are disposed in a different one of the two layer apertures and are each electrically connected to the electrically conductive patterns through conductive bumps formed on the laser diode and the photo detector. An insulation plate, having a plurality of plate apertures formed through portions of the insulation plate adjacent to the electrically conductive patterns, is coupled to the lower surface of the substrate. One of a plurality of conductive pins electrically connected with the electrically conductive patterns is fitted in each of the plate apertures of the insulation plate and extends downward from the insulation plate. An integral metal cap is attached to upper and side portions of the substrate to protect the substrate, the laser diode, and the photo detector from the outside environment. The metal cap has an opening formed in its ceiling. A glass is attached below the opening to enabling light from the laser diode to be transmitted through the glass to an exterior device and from an exterior device to the photo detector.
In one embodiment of the present invention, the layer apertures are formed from layer aperture first portions at an upper portion of the layer apertures and from layer aperture second portions at a lower portion of the layer apertures. The layer aperture first portions and layer aperture second portions are in optical communication and the layer aperture first portions have diameters smaller than the diameters of the layer aperture second portions. With the configuration of this embodiment, boundary surfaces disposed between the layer aperture first portions and the layer aperture second portions are formed. Advantageously, part of the electrically conductive patterns may be formed on the boundary surfaces allowing closer optical coupling between the optical fiber and the laser diode and the optical fiber and the photo detector. The overall thickness of the semiconductor package is also reduced.
The present invention is best understood by reference to the following detailed description when read in conjunction with the accompanying drawings.